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Enhanced Weathering of Minerals

Layered ultramafic olivine rock, Duke Island, Alaska

During Earth’s 3.7 billion-year journey, rocks have sequestered many trillions of tons of carbon dioxide. Natural rock weathering removes approximately 1 billion tons of atmospheric carbon dioxide annually. Various types of silicate rock on the surface of the earth are weathered by carbon dioxide and dissolved in rainwater, which transforms the carbon dioxide into inorganic carbonates. These carbonates find their way into streams, rivers, and oceans, eventually becoming calcium carbonate.

Enhanced weathering of minerals refers to technologies that hasten this process sustainably. One type of silicate that would work well is olivine, a greenish mineral, rich in magnesium and iron. Enhanced weathering would involve mining and milling olivine and then applying the resulting rock powder to land and water, so that the soil, oceans, and biota can act as “reactors” for accelerated weathering.

The rock powder could be strategically distributed over various landscapes, using existing infrastructure for the management of farm and forest soils. Agricultural land in the tropics, where soils are warmer and wetter and have fewer minerals that would inhibit dissolution, are ideal. If applied to one-third of tropical land, olivine could lower atmospheric carbon dioxide by 30 to 300 parts per million by 2100.